I am trying to understand the physics behind a golf ball's trajectory and have come across TrajectoWare.

How do you treat spin decay in TrajectoWare? John Adams' model as presented in his 2004 lecture does not seem to take spin decay into account, yet TrajectoWare's calculations gives a final spin that is less than the initial spin, so there must be some mechanism of spin decay. Thank you for providing TrajectoWare and your help.